Many helicopter performance factors are affected by the actual gross weight at which a helicopter is being operated. To make the best use of an aircraft and to avoid unsafe operation, it is important for the pilot to have reasonably accurate knowledge of the gross weight of the aircraft and load. Closely related, and also important, is the knowledge of the center of gravity location relative to aircraft limitations.
Attempts have been made to develop an on-board aircraft weighing system which will provide a direct indication of gross weight and the center of gravity of the aircraft. Attempts have also been made to measure gross weight by using various sensors installed in and on the landing gear of an aircraft. For aircraft using oleo strut type landing gears, attempts have involved the use of pressure transducers to measure the oleo pressure. Because of friction in the oleo strut, this approach has not provided the necessary accuracy in determining gross weight. Load transducers have been proposed in various systems to eliminate friction, but these approaches have been complex, involving increased weight with marginal accuracy.
Additional approaches to measuring gross weight have involved the use of strain gauges. Strain gauges have been installed directly on existing parts of the landing gear as well as being placed inside axle shafts using collet arrangements. However, accuracy has been poor due to low strain levels during normal operation.
Therefore, a need has arisen for a landing gear load sensor for use in an on-board weighing system which provides an accurate measurement of the gross weight of an aircraft. More particularly, a need has arisen for a strain gauged landing gear load transducer which operates at strain levels that are sufficiently high to produce an accurate measurement of critical shear load while being insensitive to other loads. Further, a need has arisen for a landing gear load sensor that is light weight and can be adapted to various types of landing gear configurations.